Automobile and other vehicle ignition key systems typically provide a mechanical key which is required to bridge an otherwise open portion of the ignition circuit. This type of key system, although quite traditional and recently coupled with steering wheel locking mechanisms, is nevertheless subject to bridging or "jumping" by thieves. With the advent of electronics, systems have been developed utilizing a complicated key card or other device having a multiplicity of connections with a dashboard receiving socket or receptacle which in one fashion or another provides an electronic or electrical code to a decoder within the automobile, thus enabling the ignition. These keys ordinarily have at least one contact per digit of code, plus power contacts.
However typically these devices suffer from the drawback of having a rather complicated and perhaps delicate key, and also are subject to decoding by means of high velocity scanning devices which are not at all a rarity among electronic buffs. In addition there is the obvious degree of complexity of circuitry involved in this type of disenabling mechanism. Most importantly however, is the fact that these systems can be jumped or hot wired. They lack the degree of integration with the system they are trying to protect that is required to make their circumvention impossible.